It was eventually marked as a "missed test" - three of those would result in a Usada doping violation.

At the time of publication of the Deadspin article, Williams had been tested more than twice as many times as other top American players - male or female - including US Open champion Sloane Stephens (one) and sister and multiple Grand Slam winner Venus Williams (two).

Williams was asked about the findings of the report during Wimbledon earlier this summer.

"I never knew that I was tested so much more than everyone else," said the seven-time champion, who lost to German Angelique Kerber in the final.

"Until I read that article I didn't realise it was such a discrepancy with me as well as against the other players that they listed, at least the American players - both male and female."

It is understood that the doping test Williams claimed in her tweet to have had on Tuesday was not conducted by Usada.